In the processing of tubular knitted fabric, it is common to pass the tubular fabric over an internal spreader, which distends the fabric tube laterally to relatively flat form and uniform width. When processed in "dry" condition, the fabric is often steamed while on the spreader, and then discharged directly into a processing station, such as a pair of calender rolls, a compressive shrinkage station, or the like. In some cases, the spread fabric is discharged from the spreader into a wet processing apparatus, such as a pad. Representative forms of prior art spreaders are reflected in, for example, the Robert Frezza U.S. Pat. No. 3,875,624 and in the S. Cohn et al U.S. Pat. No. 2,228,001. In those representative spreading apparatuses, a spreader frame comprises spaced, opposed spreader frame sections, typically carrying movable belts which engage the inner edge walls of the distended fabric.
At the transverse working axis of the spreader frame, there are provided opposed pairs of so-called radius rolls which engage through the fabric wall with grooved edge drive rolls. When the edge drive rolls are moved laterally into contact with a horizontally disposed spreader frame, the spreader frame is positioned and supported both vertically and horizontally by the inter-engaging geometry of the external edge drive rolls and the internal pairs of radius rolls.
Typically, the width of a tubular fabric spreader is adjustably established by means of an internal spacer bar, extending from one side to the other of the frame along the transverse working axis, and various arrangements have been provided in the prior art apparatus for adjusting the length of the spacer bar. One advantageous form of such adjustment is reflected in the S. Cohn et al U.S. Pat. No. 2,228,001. The mechanism includes a movable latch lever, which may be gripped by the hand, to permit telescopic movement of elements of the spacer bar.
In prior art equipment of which the applicant is aware, it has always been necessary to stop the processing line in order to effect width adjustment of the spreader frame. This is required by the fact that the spreader is completely enclosed by the moving tubular fabric, and the only way that access can be gained to the internal mechanism is through the wall of the fabric. Once the processing line has been stopped, it is usually possible to manipulate the adjusting mechanism by distorting the wall of the fabric, working by "feel". In some cases, however, it is necessary to cut an opening in the fabric in order to make a width adjustment.
Even in cases where it has not been necessary to cut or distort the fabric, the practical problems involved in temporarily stopping the processing line for width adjustment of the spreader seriously discourage the making of any such adjustments during a processing run. In this respect, if the fabric is held motionless for a period of time in a processing stage, such as a calender, compactor or pad, the fabric may be off specification in the area exposed to excessive time in the processing stage, and may have to be cut out and discarded. Under the best of circumstances, width adjustment involves at least an undesirable and time-consuming interruption in an otherwise continuous processing operation.
Efforts in the past have been made to provide automatic adjustment by utilization of spring arrangements in conjunction with the spacer bar, urging the opposite side of the spreader frames in a separating direction. These arrangements have proved impractical, however, because effective spring force decreases markedly with increasing width, while, in general, greater force is required to retain the spreader frames at wider widths than at narrower widths.
Pursuant to the invention, a novel and improved spreader frame structure is provided, in which a relatively constant force yieldable means is provided for yieldably maintaining separation of the spreader frames, in a manner accommodating expansion and contraction of the spreader width, under the control of the external edge drive rolls, within a reasonable range of adjustment, and without excessive variation in contact pressure on the fabric wall which is interposed between the radius rolls and the edge drive rolls. More particularly, the apparatus of the invention includes a spreader frame in which the opposed spreader frame elements are connected by a telescopic spacer assembly, urged in an extending or widening direction by a so-called gas spring which, within the limits of its extension, has a reasonably uniform range of extending force. The arrangement is such that, within the range of operation of the telescoping spacer unit, the width of the spreader frame may be effectively controlled by increasing and decreasing the spacing of the external edge drive rolls. This may be accomplished as an in-process adjustment, either manually or from a remotely located control station. Moreover, the arrangement lends itself to automatic, continuous width monitoring and adjustment, in order to achieve greater uniformity in the processed width of the fabric.
In its simplest form, the spreader apparatus of the invention incorporates a telescopic spacer assembly, which extends between opposed spreader frame sections at the transverse working axis and serves to provide mechanical alignment of the frame sections to maintain the sections substantially in parallel relation. Associated with the telescoping assembly is an extendable gas spring unit, which is connected so as to be isolated from non-axial forces and which is contained within a telescoping type of housing structure, so as to be free of contact with the fabric passing over the spreader. Typically, a spreader or frame installation may be provided with a series of two or three spacer units of graduated size ranges covering the full width capacity of the processing line. The operating range of any one of the units is sufficient to accommodate automatic width adjustment during the processing of a given fabric, but it may be necessary or desirable to exchange spacer units when the processing line is set up to handle a different type or size of fabric, as will be understood. In this respect, the yieldable spacer units are adapted for quick-disconnect association with the primary spreader frame sections, so that changeover of the equipment for processing different types of fabric may be accomplished in an expedited manner.
In a particularly advantageous specific form of the invention, the yieldable telescopic spacer unit is comprised of a pair of telescopically interfitting tubular sections, which may be of irregular cross section, which serve not only to enclose and protect the gas spring unit, but also to provide mechanical support for the spreader frame sections against translational displacement. Where the tubular sections are of irregular cross section, they serve additionally to resist rotational displacement. In another advantageous form of the invention, structural support of the spreader frame sections is provided by spaced, telescopically associated elements straddling the gas spring element, and the entire telescopic structure, including the gas spring, is enclosed within a flexible, bellows-type housing.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.